1. Field of the Invention
The present invention concerns a display screen allowing for the visual dislay of the contour of a screen and a method for controlling such a screen.
2. Discussion of the Background
This invention can generally be applied to optical image formation uses in various spheres (scientific, professional or medical) and in the metrology of the image.
A display screen according to the prior Art is described in FIG. 1. The one represented includes:
a first substrate 10 covered with a matrix of control electrodes Eij defining so many pixels and covered with addressing lines Li and addressing columns Cj suitable for addressing a suitable voltage onto each electrode Eij, PA1 a second substrate 20 covered with a counterelectrode CE, PA1 between the two substrates 10 and 20, an electrooptical material 30, such as a liquid crystal film. PA1 for a first frame parity (e.g. even), either a voltage of a first type, e.g. of the form Vid (1+k)+C, or a voltage of a second type, e.g. of the form Vid (1-k)-C, PA1 for a second frame parity (e.g. odd), either a voltage of the second type, e.g. of the form Vid (1-k)-C, or a voltage of the first type of the form Vid (1+k)+C
A transistor Tij is placed at each crossing of an addressing line Li and an addressing column cj.
The application of certain voltages to the lines and columns allows for the displaying of an image point by point or line by line.
In certain professional fields, it is often necessary to extract from a bidimensional image the characteristics of certain represented objects. It is then practical to make the contours of these images appear.
Up until now, this has required the use of a specialized computer for contour extraction, but these calculation means add to the price of the equipment.